1. Technical Field
The present invention relates to a solvent that is biodegradable and generally benign to human health, and more particularly to a mixture of a lactate ester and D-limonene; the mixture provides effective solvency for a broad range of tasks. This blended solvent is shown to provide effective performance for solvent applications, including cleaning applications, that provides for a non-toxic, cost effective alternative to commonly used toxic solvents from a renewable biological feedstock.
2. Background Art
Solvents derived from renewable biological feedstocks that are non-toxic and have very good environmental properties are becoming highly desirable for replacement of many halogenated or other toxic solvents.
Ethyl lactate and other lactate esters are environmentally benign, non-toxic solvents derived from renewable carbohydrates via fermentation and separations processes.
D-limonene is a biodegradable cleaning solvent and degreaser occurring in nature as the main component of citrus peel oil. These user-friendly characteristics encourage the use of d-limonene in solvent applications. However, d-limonene lacks some physical properties that limit its applicability to more widespread use.
D-limonene is not water-miscible and consequently not easily water-rinsable and is considered a non-aqueous cleaning solvent. D-limonene is a slow-drying solvent, that does not quickly evaporate off of surfaces to which it has been applied. The art does not teach how to address these problems with d-limonene that would permit extending the applicability of d-limonene as a solvent to a wider variety of solvent applications.
Lactate esters have complementary physical properties where d-limonene is lacking. Ethyl lactate is very water-miscible and has high solvating power to dissolve oxygenated chemicals and resins and to remove dried inks, paints, and coatings. However, ethyl lactate lacks adequate solvating power for very hydrophobic materials such as oils and greases that d-limonene is capable of solvating. Lactate esters, particularly ethyl and methyl lactate, are faster-drying solvents than d-limonene.
The blending of ethyl lactate with d-limonene in presence of other mixture components such as surfactants, or long chain alcohols or esters or polymers has been disclosed in the art.
U.S. Pat. No. 5,372,742, teaches blending ethyl lactate and d-limonene together with cetyl acetate and optionally with propylene glycol methyl ether acetate to give a liquid, non-aqueous cleaner composition that is well-suited as a fingernail polish remover.
U.S. Pat. No. 5,360,580 discloses a blend of d-limonene, N-methyl pyrrolidone, dibasic ester and cetyl acetate. That d-limonene mixture removes fingernail polish. The ""580 patent teaches that lactate esters could be used to replace the d-limonene. The ""580 patent does not teach blending d-limonene with lactate esters.
The art teaches solvent blend compositions with lactate ester or d-limonene blended with other components such as surfactants, longer chain alcohols, esters or ethers. However, the art does not teach or suggest how to modify the limiting properties of d-limonene are used. None of these show that just blending just these two biologically and renewable resource derived components, ethyl lactate and d-limonene could lead to solvent blend compositions with very desirable properties for many widespread applications.
D-limonene alone is often unsuitable for electronic and precision parts cleaning, where high purity solvents are typically used and water rinsability is often desired. Solvents used for these cleaning applications cannot leave residues. The addition of surfactants to solvents for use in electronic and precision parts cleaning is not acceptable for enhancing solvent rinsability, because surfactants tend to leave residue.
In many other cleaning applications, water miscibility is important. Being able to rinse a solvent-cleaned surface with water after the solvent cleaning step is preferable to rinsing with an organic solvent. Furthermore, aqueous rinses are often easier to handle and dispose of after application. Thus, water rinsability is highly desirable in a cleaning solvent for economic and environmental reasons.
Many pesticide and herbicide formulations require solvents that have very good solvating power for the active compounds as well as stability and dispersability. By having environmentally sound and non-toxic solvent blends to make pesticide and herbicide formulations could replace many of the currently used toxic solvents that are routinely sprayed on the crops in conjunction with the pesticides and herbicides.
A solvent is a substance that is generally capable of dissolving another substance, or solute, to form a uniformly dispersed mixture (solution) at the molecular or ionic level. Solvents are either polar (high dielectric constant) or non-polar (low dielectric constant). Water, the most common solvent, is strongly polar having a dielectric constant of 81. Hydrocarbon solvents are non-polar and are comprised of two groups, aliphatics such as alkanes and alcohols, and aromatics, which generally have a higher solvency power than aliphatics. Other organic solvent groups are esters, ethers, ketones, amines, nitrated hydrocarbons and halogenated hydrocarbons.
The chief uses of organic solvents include dissolution of coatings (paints, varnishes, and laquers), industrial and household cleaners, printing inks, and extractive processes. Because many solvents are flammable and toxic to health, there is a need to develop safer solvents for commercial use without sacrificing critical performance.
For decades industrial and household cleaning products have been utilized to provide certain tasks such as paint removers, ink removers, degreasers, etc. Solvents are also used to clean, maintain, and prepare wood, metal, masonry, natural and synthetic fabrics, plastic components, electronic components. Although providing the needs of these many and mission-critical tasks, most solvents generally, are toxic, thus posing a threat to health and to the environment. These environmental and health threats include ozone depleting air pollutants and water pollution that threaten aquatic organisms and drinking water supplies. Many of these solvents are carcinogenic and hazardous to health in general.
Although government, industry and the community at large are all relatively well informed to the dangers of toxic solvents, the dangers associated with the use of such solvents have not dramatically diminished their use. Safer handling, disposal, recycling, recovery and other responsible methods of dealing with toxic substances are improving. However, the availability of safer alternative solvents is still not wide spread, especially in second and third world countries, which is due, primarily, to the high cost of the solvent alternatives and because the majority of the environmentally safer solvent alternatives do not provide satisfactory performance.
In order for an xe2x80x9cenvironmentally friendlyxe2x80x9d solvent alternative to gain wide spread acceptance, a solvent should meet several criteria. First, it should provide effective performance. Second, it should be economically viable and affordable. Third, it should be widely available and, of course, it should be non-toxic to the environment generally and humans specifically.
Several alternative solvents have been introduced by industry for decades, but in general do not meet the criteria stated above. Further, many of these solvents are not completely biodegradable, just less toxic.
A solvent described hereinafter provides high solvency performance while overcoming the toxicity issues associated with most other organic solvents. In addition, a contemplated solvent is biodegradable.
The present invention contemplates an environmentally friendly solvent from renewable biological resources. This solvent consists essentially of d-limonene and lactate esters.
A contemplated solvent composition consists essentially of about x weight percent C1-C4 ester of lactic acid, where x is about 20 to about 80; and about 100xe2x88x92x weight percent of d-limonene (CAS Nos: 5989-27-5, 94266-27-4 and 68647-72-3).
In one preferred embodiment, the composition comprises:
(A) about 20 to about 40 weight percent of a C1-C4 ester of lactic acid; and
(B) about 100-20 to 100-40 weight percent of d-limonene.
In each of the embodiments of the invention, the particularly preferred C1-C4 ester of lactic acid is the ethyl ester so that ethyl lactate is also particularly preferred.
The present invention has several benefits and advantages.
One benefit of the invention is that a contemplated composition is much safer than a halogenated organic solvent.
An additional advantage of the present invention is that the cleaning solvent is partially miscible with water, and thus can be removed with water rinsing, including high pressure water. This rinsing factor can offer some industrial advantages that do not exist with traditional cleaning solvents.
Yet another benefit of a preferred embodiment of the present invention is that it is biodegradable, non-toxic and is derived from renewable biological feedstocks.
Still further benefits and advantages will be apparent to the skilled worker from the discussion that follows.